The present invention relates to backing blocks, transducer arrays and methods for survivability. In particular, a shaped backing block may avoid thermal tension damage to a transducer array during manufacturing, testing or use.
As part of development or manufacturing, transducer arrays are temperature stress tested. As part of use, similar temperature stresses are placed on a transducer array. For example, the transducer arrays are subjected to thermal variation. Due to usage, storage or shipping, the transducer may be exposed to a range of temperatures. Tests typically span a −30° to +60° Celsius temperature range. Other temperature ranges may be used. The transducer array is subjected to this range of temperatures over a number of cycles, such as 60 cycles. During use or shipping, the transducer may be subjected to various temperatures any number of times.
Differences in a thermal coefficient of expansion between different materials within a transducer stack may result in damage to the array from temperature changes. For example, piezoelectric ceramic material is very strong in compression but very weak in tension. Soft or semi-rigid backing material connected with the piezoelectric ceramic has very high thermal expansion relative to the other materials in the array. The backing block material may heave or bulge due to heat to a greater extent than the ceramic material, causing damage to the transducer array. Due to the large thermal expansion of the backing block, the piezoelectric ceramic may crack. Cracked elements have weak or less desirable acoustic response.